L-tartaric acid salt of a (1R) diastereomer of a 2-azadihydroxybicyclo 2.2.1!heptane compound and the preparation of 2-azabicyclo 2.2.1!heptane compounds

ABSTRACT

A method for the preparation of a lactam compound of formula ##STR1## wherein R&#39; 1  and R&#34; 1  independently are acyl or aroyl, or taken together form an optionally substituted methylene, and G 1  is hydrogen or an amino protecting group, comprising oxidizing a bis O-protected 1R-2-azadihydroxybicyclo- 2.2.1!heptane compound of formula ##STR2## with about 0.1 mol % to about 1 mol % of RuO 2  or hydrate thereof in the presence of about 3 equivalents of an oxidant to form the lactam compound with an enantiomeric excess of greater than or equal to about 95%.

This application is a divisional of U.S. patent application Ser. No.08/732,024, filed Oct. 16, 1996, now U.S. Pat. No. 5,684,159 which inturn is a continuation-in-part of U.S. patent application Ser. No.08/655,395, filed May 30, 1996, now U.S. Pat. No. 5,670,649 which inturn is a continuation-in-part of U.S. patent application Ser. No.08/476,156, filed Jun. 7, 1995, now U.S. Pat. No. 5,631,383, issued May20, 1997.

FIELD OF THE INVENTION

The present invention is directed to a method for preparing a2-azadihydroxybicyclo 2.2.1!heptane compound. The invention is alsodirected to an L-tartaric acid salt of the (1R) diastereomer of the2-aza-dihydroxybicyclo 2.2.1!heptane compound and its preparation. Inaddition, the invention is directed to a method for bis O-protection ofthe (1R) diastereomer of the 2-azadihydroxybicyclo 2.2.1!heptanecompound and a method for oxidizing derivatives of the (1R) diastereomerof the 2-azadihydroxy-bicyclo 2.2.1!heptane compound to a correspondinglactam compound.

U.S. Pat. No. 5,284,769 discloses that a lactam compound, whichencompasses a lactam compound prepared according to the invention, asbeing a useful synthon for preparing pharmaceutically active agents. J.Chen et al., Tet. Lett., 30 5543 (1989) disclose a lactam compound,which encompasses a lactam compound prepared according to the invention,as being used in preparing a compound that is active as an adenosineagonist.

Reported Developments

C. K. -F. Chui, Syn. Comm., 26(3), 577 (1996) discloses resolving adiastereomeric mixture of bicycloheptenamine compounds of formulae (i)and (ii) ##STR3## using L-dibenzoyl tartaric acid, i.e., by fractionalcrystallization. The Chui reference does not disclose means forresolving bishydroxylated products of the diastereomeric mixture.

S. J. C. Taylor et al., Tetrahedron: Asymmetry, 4(6), 1117 (1993)disclose the enzymatic resolution of a lactam of formula (iii) ##STR4##to yield the enantiomers of formulae (iv) and (v) ##STR5## S. J. C.Taylor et al. do not disclose any means for resolving bishydroxylatedproducts of the lactam (iii).

U.S. Pat. No. 5,284,769 discloses the enzymatic resolution of a lactamof formula (vi) ##STR6## to yield the enantiomers of the lactam. U.S.Pat. No. 5,284,769 does not disclose any means for resolvingbishydroxylated products of the lactam (vi).

SUMMARY OF THE INVENTION

A method according to the invention is directed to the preparation of a2-azadihydroxybicyclo 2.2.1!heptane compound of formula ##STR7##wherein * represents an R chirality, *' represents an S chirality, R ishydrogen or, respectively, a group of formula ##STR8## wherein R₁, isalkyl and Ar is optionally substituted aryl, comprising bishydroxylatinga bicyclo 2.2.1!heptene compound of formula ##STR9## wherein *, *' and Rare as previously defined, in the presence of about 0.1 mol % to about 5mol % of a metal osmate compound or about 0.06 mol % to about 0.07 mol %osmium tetroxide, and an oxidizing agent capable of regenerating osmiumtetroxide.

The invention is also directed to the treatment of the (1R) diastereomerof the 2-azadihydroxybicyclo 2.2.1!heptane compound (I) wherein R is agroup of formula II with L-tartaric acid, and the L-tartaric acid saltproduct thereof. Furthermore, the invention is directed to using the(1R) diastereomer of the 2-azadihydroxybicyclo 2.2.1!heptane compound orsalt thereof in an acid facilitated acetalizing or ketalizing reactionthat results in the protection of the dihydroxy moieties thereof inisopropanol. In addition, the invention is directed to oxidizing a bisO-protected derivative of the (1R) diastereomer of the2-azadihydroxybicyclo- 2.2.1!heptane compound to a corresponding lactamcompound in the presence of about 0.01 mol % to about 1 mol % of RuO₂ orhydrate thereof with about 3 equivalents of an oxidant to form thelactam compound in an enantiomeric excess ("ee") of greater than orequal to about 95%.

DETAILED DESCRIPTION OF THE INVENTION

As used above, and throughout the description of the invention, thefollowing terms, unless otherwise indicated, shall be understood to havethe following meanings. "Alkyl" means an aliphatic hydrocarbon groupwhich may be straight or branched having 1 to about 4 carbon atoms.Exemplary alkyl groups include methyl, ethyl, i-propyl and t-butyl."Optionally substituted methylene" means --CH₂ -- or that moiety whereinthe hydrogen atoms are replaced individually by one or two groups, whichmay be identical or different, selected from alkyl or phenyl, orreplaced concomitantly to form, together the carbon atom of themethylene, cycloalkyl.

"Aryl" means optionally substituted phenyl or optionally substituted α-or β-naphthyl. A substituted aryl is substituted by one or more arylgroup substituents, which may be identical or different, which includehalo, alkyl, alkoxy, and nitro.

"Alkoxy" means an alkyl-O- group wherein the alkyl group is aspreviously described. Exemplary alkoxy groups include methoxy, ethoxy,i-propoxy and t-butoxy.

"Cycloalkyl" means an aliphatic cyclic ring of about 5 to about 6 carbonatoms. An exemplary cycloalkyl group is cyclohexyl.

"Acyl" means an alkyl-CO- group wherein the alkyl group is as previouslydescribed. Exemplary acyl groups include acetyl and propanoyl .

"Aroyl" means an aryl-CO- group wherein the aryl group is as previouslydescribed. An exemplary aroyl group is benzoyl.

"Halo" means fluoro, chloro, bromo or iodo. Preferred are fluoro andchloro.

"Oxidizing agent capable of regenerating osmium tetroxide" means anoxidant that will oxidize the osmium of the metal osmate (Os⁺⁶) toosmium tetroxide (Os⁺⁸) or reoxidizes the osmium tetroxide reduced ineffecting the bishydroxylation to osmium tetroxide (Os⁺⁸). Examples ofoxidizing agents capable of regenerating osmium tetroxide includeN-methylmorpholine oxide or triethylamine oxide and potassiumferricyanide (K₃ FeCN₆), preferred is N-methylmorpholine oxide.

"Metal osmate" means a salt compound formed from M^(n+), a metal cationwherein n is 1 or 2, and an osmium oxide anion complex OsO₄ !⁻², orhydrates thereof. Preferable metal osmates are alkali or alkaline earthosmates, including sodium, potasium, rubidium, cesium, calcium andbarium osmates, more preferable is K₂ OsO₄.2H₂ O. Examples of methodsuseful for preparing metal osmates are described by B. N. Ivanov-Emin etal., Zh. Neorg. Khim. 31(5) 1238 (1986), H. C. Jewiss, J. C. S. DaltonTrans. 199 (1985), B. N. lvanov-Emin et al., Zh. Neorg. Khim. 29(4) 1241(1984), B. N. Ivanov-Emin et al., Zh. Neorg. Khim. 28(5) 1246 (1983).

"Salt thereof" means the compound with a basic moiety neutralized by anacid to form the corresponding acid addition salt. Acids which can beused to prepare the acid addition salts include preferably those whichproduce, when combined with the free base, pharmaceutically acceptablesalts, that is, salts whose anions are non-toxic to a patient, and sothat subsequent use of the acid addition salt does not proscribe thesalt from subsequent chemical reactivity. The acid addition salt isuseful for example as a source for the regeneration of the base compoundtherein by treatment with a base such as alkali, for purposes ofpurification and/or identification, or for interconversion to anotheracid addition salt form by an ion exchange procedures. Examples of acidaddition salts include those encompassing the following acids: mineralacids such as hydrobromic, hydrochloric acid, sulfuric acid, phosphoricacid and sulfamic acid; and organic acids such as acetic acid, citricacid, lactic acid, tartaric acid, dibenzoyltartaric, malonic acid,succinic, 2,3-dimethoxysuccinic, methanesufonic acid, ethanesulfonicacid, benzenesulfonic acid, p-toluenesulfonic acid, cyclohexylsulfamicacid, quinic acid, and the like.

PREFERRED EMBODIMENTS

A special embodiment for the bishydroxylation method according to theinvention, is that wherein R is a group of formula II or II'.

A preferred embodiment for the bishydroxylation method according to theinvention, is that wherein R₁ is methyl or ethyl, and Ar is optionallysubstituted phenyl, which when substituted is substituted by one or moremethyl or methoxy.

A more preferred embodiment for the bishydroxylation method according tothe invention, is that wherein R₁ is methyl, and Ar is phenyl.

A preferred embodiment for effecting the bishydroxylation uses theosmium tetroxide at about 0.06 mol % to about 0.07 mol %, morepreferably at about 0.06 mol %.

Another preferred embodiment for effecting the bishydroxylation uses themetal osmate at about 0.1 mol % to about 5 mol %, more preferably atabout 0.2 to about 0.5 mol %.

Yet, another preferred embodiment for effecting the bishydroxylationuses an alkali or alkaline earth osmate as the metal osmate, morepreferably K₂ OsO₄.2H₂ O.

A special embodiment for preparing the L-tartaric acid salt of the (1R)diastereomer of the 2-azadihydroxybicyclo 2.2.1!heptane compound, i.e.,##STR10## according to the invention, is that wherein R is a group offormula II.

A preferred embodiment for preparing the L-tartaric acid salt of the(1R) diastereomer of the 2-azadihydroxybicyclo 2.2.1 !heptane compoundaccording to the invention, is that wherein R₁ is methyl and Ar isphenyl.

Another special embodiment according to the invention is for preparingthe L-tartaric acid salt of the (1R) diastereomer of the2-azadihydroxybicyclo- 2.2.1!heptane compound in a substantiallyenantiomerically purified state in the presence of a (1S) diastereomerof the 2-azadihydroxybicyclo 2.2.1!-heptane compound.

A preferred embodiment for preparing the L-tartaric acid salt of the(1R) diastereomer of the 2-azadihydroxybicyclo 2.2.1 !heptane compoundaccording to the invention, is that wherein the preparation occurs in anaqueous-organic solvent mixture.

A more preferred embodiment for preparing the L-tartaric acid salt ofthe (1R) diastereomer of the 2-azadihydroxybicyclo 2.2.1!heptanecompound according to the invention, is that wherein the organic solventis isopropanol (IPA).

An even more preferred embodiment for preparing the L-tartaric acid saltof the (1R) diastereomer of the 2-azadihydroxybicyclo 2.2. 1 !heptanecompound according to the invention, is that wherein the preparationoccurs in an aqueous-IPA solvent mixture having a volume ratio of about30:70 to about 15:85, further preferably of about 25:75.

A special embodiment for the acid facilitated acetalizing or ketalizingreaction method according to the invention, is directed to a method forpreparing a compound of formula IV ##STR11## wherein R is as definedherein, R_(3'), and R_(3") are hydrogen, alkyl or phenyl, or R_(3') andR_(3") taken together with the carbon atom to which they are attachedform a cycloalkyl, comprising acid facilitated acetalizing or ketalizingof a compound of formula V ##STR12## wherein R_(4') and R_(4") arealkoxy, or taken together with the carbon atom to which they areattached form carbonyl, with the (1R) diastereomer of the2-aza-dihydroxybicyclo 2.2.1!heptane as described herein or salt thereofin IPA.

A preferred embodiment for the acid facilitated acetalizing orketalizing reaction is that wherein R_(4') and R_(4") are methoxy andR_(3') and R_(3") are methyl.

Another preferred embodiment for the acid facilitated acetalizing orketalizing reaction is that wherein the acid facilitation is effectedusing trifluoroacetic acid (TFA).

Yet another preferred embodiment for the acid facilitated acetalizing orketalizing reaction is that wherein R is a group of formula II.

A more preferred embodiment for the acid facilitated acetalizing orketalizing reaction is that wherein R₁ is methyl and Ar is phenyl.

Still another preferred embodiment for the acid facilitated acetalizingor ketalizing reaction is that wherein the (1R) diastereomer of the2-azadihydroxybicyclo 2.2.1!heptane compound is in the form of anL-tartaric acid salt thereof.

A special embodiment for the lactam preparative method according to theinvention, is directed to a method for preparing a lactam compound offormula VI ##STR13## wherein R'₁ and R"₁ independently are acyl oraroyl, or taken together form an optionally substituted methylene, andG₁ is hydrogen or an amino protecting group, comprising oxidizing a bisO-protected (1R) diastereomer of the 2-aza-dihydroxybicyclo2.2.1!heptane compound of formula VII ##STR14## in the presence of about0.1 mol % to about 1 mol % of RuO₂ or hydrate thereof with about 3equivalents of an oxidant to form the lactam compound with an ee ofgreater than or equal to about 95%.

A preferred embodiment for the lactam preparative method is that whereinthe RuO₂ is present at about 0.5 mol %.

Another preferred embodiment for the lactam preparative method is thatwherein the lactam compound is formed with an ee of greater than orequal to about 99%.

General parameters for the preparative methods are those describedheretofore and below.

In general, the bishydroxylation is carried out under the conditionsdescribed by V. VanRheenen et al., Tetrahedron Letters, Vol. 23,1973-1976 (1976). The oxidant must effect the bishydroxylation in theexo form. More particularly, the oxidation can be carried out by meansof potassium permanganate or osmium tetroxide or a metal osmate andworking in the presence of N-methylmorpholine oxide or triethylamineoxide or potassium ferricyanide (K₃ FeCN₆).

According to the invention the osmium tetroxide is employed in acatalytic amount which results in a more effective control of osmiumresidues in the product. The reaction with the osmium may occur with aslittle as about 0.06 mol% to about 0.1 mol% which takes respectivelyfrom about 21 to about 5 hours. The reaction preferably takes place withabout 0.06 mol% osmium tetroxide. The oxidation may take place in anaqueous-organic solvent medium such as water-t-butanol or water-acetone,more preferably water-acetone. An ether solvent such as t-butyl methylether or di-i-propyl ether may additionally be present when theoxidation is carried out in an water-acetone solvent medium. A preferredrange of volume amounts of ether:acetone:water solvent mixture is about1.9:16.7:1 of ether/acetone to about 11.1:7.4:1; more preferred is11.1:16.7:1 to 16.7:16.7:1.

The bishydroxylation can also be effected in the same manner on amixture of the diastereomers (I) and (I'), i.e., without them having tobe separated before effecting the bishydroxylation.

The (1R) diastereomer of formula I, wherein R is a group of formula II,can be isolated as salts of optically-active organic acids, and moreespecially from a mixture of diastereomeric compounds of formulae I andI' by diastereo-selective crystallization using such optically-activeorganic acids. One useful optically-active organic acid isL-dimethoxysuccinic acid. The salt formation using L-dimethoxysuccinicacid is carried out in an appropriate organic solvent such as a ketoneor an aliphatic alcohol, particularly advantageous is IPA. According tothe invention, L-tartaric acid is another useful optically-activeorganic acid. The salt formation using L-tartaric acid acid is carriedout in a solvent such as an aqueous-organic solvent mixture wherein theorganic solvent such as an aliphatic alcohol such as IPA. The use ofL-tartaric acid results in improved yields and enantiomeric purity ofthe desired diastereomer (I).

The dihydroxy moieties of a compound of formula I, wherein R is hydrogenor a group of formula II, can be protected in the form of an ester oracetal/ketal to yield a product of formula VIII ##STR15## wherein R ishydrogen or a group of formula II, and R'₁ and R"₁ are as definedbefore.

In general, the protection of the hydroxy groups is achieved undereither esterification or acetalization/ketalization conditions. Forexample, esterification takes place by reacting an acyl containing groupsuch as acetic acid or propionic acid in the presence ofp-toluenesulfonic acid in an organic solvent such as an aromatichydrocarbon, for example, benzene or toluene, by separating the watergradually, for example azeotropically, as it is formed. For example,acetalization/ketalization is effected by reacting an aldehyde or aketone, possibly in the form of ketal, in the presence of an acid suchas TFA in an organic solvent such as an aliphatic alcohol, for example,IPA, aromatic hydrocarbon, for example, benzene or toluene, or ether,for example, t-butyl methyl ether or di-i-propyl ether, at about 50° C.to about the boiling point of the reaction mixture. When an ethersolvent is used acetic may acid may also be present which results information of a salt of the compound of formula IV that is extractable inwater. A preferred ketalization medium, according to the invention,comprises the use of 2,2-dimethoxypropane, TFA and IPA to give improvedyield and enantiomeric excess of the product. The reaction takes placeat about 70° C.

The product of formula VIII wherein R is a group of formula II can betransformed into a product of formula VIII wherein R is hydrogen byhydrogenolysis. In general, the hydrogenolysis is carried out by meansof hydrogen, which is optionally pressurized, in the presence of acatalyst such as palladium on charcoal in an organic solvent such as analcohol, for example, methanol, ethanol or IPA, at about 0° C. to about500° C. A product of formula VIII wherein R is hydrogen is also beformed employing the same hydrogenolysis reagents and conditions on thesalt of the compound of formula IV wherein R is a group of formula II.

The product of formula VIII wherein R is hydrogen can be transformedinto a product of formula IX ##STR16## wherein R'₁ and R"₁ are definedas before and G₂ is an amino protecting group, by the selectiveintroduction of an appropriate protecting group.

The protecting groups are selected from those which can later be removedselectively. These protecting groups include the following, which areparticularly well suited: t-butoxycarbonyl, chloroacetyl, methoxymethyl,trichloro-2,2,2-ethoxycarbonyl, t-butyl, benzyl, p-nitrobenzyl,p-methoxybenzyl, diphenylmethyl, trialkylsilyl, allyloxycarbonyl, andbenzyloxycarbonyl groups, wherein the phenyl ring is optionallysubstituted by halo, alkyl or alkoxy. Among the protecting groups whichare particularly well suited, one can mention those described by T. W.Greene and P. G. M. Wuis, "Protecting Groups in Organic Synthesis,"Chapter 7, 2nd edition, John Wiley & Sons (1991). The t-butoxycarbonylgroup is of particular interest.

The product of formula IX wherein G₂ is t-butoxycarbonyl can be obtaineddirectly from a product of formula VIII wherein R is the group offormula II by simultaneous hydrogenolysis and t-butoxycarbonylation.

For example, the reaction is carried out by simultaneously reactinghydrogen in the presence of a catalyst such as palladium and charcoaland di-t-butyl dicarbonate with a product of formula VIII wherein R is agroup of formula II in an organic solvent such as an alcohol, forexample, methanol, ethanol or IPA, about 0° C. to about 50° C. Thisreaction is particularly useful where R'₁ and R"₁ taken together form anoptionally substituted methylene.

Alternatively, the product of formula IX wherein G₂ is t-butoxycarbonylcan be obtained in two steps from a product of formula VIII wherein R isthe group of formula II by first effecting the hydrogenolytic removal ofthe group of formula II to yield the corresponding product wherein R ishydrogen, and second effecting the t-butoxycarbonylation of thatproduct. The hydrogenolytic removal is effected as previously described,and the t-butoxycarbonylation is effected in water under alkalineconditions using (Boc)₂ O.

The product of formula IX is then oxidized into a product of formula X##STR17## wherein R'₁, R"₁ and G₂ are defined as above.

In general, the oxidation is conducted by means of ruthenium oxide(RuO₄), which can be optionally generated in situ from a precursor suchas RuO₂ or RuCl₃ in the presence of an oxidant selected from a periodatesuch as sodium periodate, a hypohalite such as hypochlorite or sodiumhypobromite or a bromate such as sodium bromate or an organic tertiaryamine oxide such as N-methylmorpholine oxide or triethylamine oxide. Thereaction takes place in a solvent such as water or a homogeneous orheterogeneous aqueous-organic medium, such as a water-EtOAc mixture.

The oxidation can also be conducted using sodium hypochlorite alone orusing potassium permanganate or sodium tungstate in the presence of anoxidant such as sodium hypochlorite, hydrogen peroxide or an alkylhydroperoxide.

The product of formula X can also be obtained by oxidation of a productof formula VIII wherein R is hydrogen under the conditions describedabove, followed by the protection of the nitrogen atom of the lactam offormula XI ##STR18## wherein R'₁ and R"₁ are defined as above, by aprotecting group as defined above.

The products of formula X and Xl are particularly useful for thepreparation of a carbo sugar of formula XII ##STR19## wherein R₂ iscarboxy, alkoxycarbonyl, N-alkylaminocarbonyl, hydroxymethyl oralkoxymethyl, and R' and R" which may be identical or different, arehydrogen, acyl or aroyl, or R'₁ and R"₁ taken together with the carbonatom to which they are attached form an optionally substituted methylenegroup whose carbon atom is optionally substituted by one or two groups,which may be identical or different, selected from alkyl or phenyl, ortwo alkyl taken together can form cycloalkyl, and G₁ is hydrogen or aprotecting group G₂ for the amino function. More particularly, R₂ is anethylaminocarbonyl group or hydroxymethyl group, and R' and R" togetherform an isopropylidene group.

The product of formula X can be transformed into a product of formulaXII under conditions which are appropriate for the nature of thesubstituent R₂ which must be introduced.

The product of formula XII wherein R₂ is carboxy can be prepared byreacting a mineral base such as NaOH with the product of formula X,followed by the replacement of the protecting group G₂ by hydrogen andoptionally groups R'₁ and R"₁ by hydrogen.

The product of formula XIl, wherein R₂ is carboxy, can be obtained bythe replacement of the protective group G₂ of formula X with a hydrogenatom, followed by the action of a mineral base such as sodium carbonate,and optionally replacing the radicals R'₁ and R"₁ by hydrogen.

The product of formula XII wherein R₂ is alkoxycarbonyl can be preparedby reacting an alkali metal alkoxide with the product of formula X,followed by the replacement of the protecting group G₂ by hydrogen andoptionally of the groups R'₁ and R"₁ by hydrogen.

The product of formula XII, wherein R₂ is alkoxycarbonyl can be obtainedby the replacement of the protective group G₂ of the product of formulaX by hydrogen, followed by the action of an alkali metal alkoxide, andoptionally replacing the radicals R'₁ and R"₁ by hydrogen.

The product of formula XII wherein R₂ is N-alkylaminocarbonyl can beprepared by reacting an alkylamine with the product of formula X,followed by the replacement of the protecting group G₂ by hydrogen andoptionally of the groups R'₁ and R"₁ by hydrogen.

The product of formula XII, wherein R₂ is N-alkylaminocarbonyl, can beobtained by the replacement of the protective group G₂ of the product offormula X by hydrogen, followed by the action of an alkylamine, andoptionally replacing the radicals R'₁ and R"₁ by hydrogen.

The product of formula XII wherein R₂ is a hydroxymethyl group can beprepared by reacting a reducing agent such as a borohydride, forexample, sodium or potassium borohydride, with the product of formula X,followed by the replacement of the protecting group G₂ by hydrogen andoptionally of the groups R'₁ and R"₁ by hydrogen.

The product of formula XIl, wherein R2 is a hydroxymethyl radical, canbe obtained by replacement of protective group G₂ of the product offormula X by a hydrogen atom, followed by the action of a reducing agentsuch as sodium or potassium borohydride, and optionally replacing theradicals R'₁ and R"₁ by hydrogen.

The present invention also encompasses the isolation of the (1S)diastereomer of the compound of formula I' using optically-activeorganic acids of the opposite configuration to those described forisolating the (1R) diastereomer of the compound of formula I. Accordingto the invention, the (1S) diastereomer of the compound of formula I'can then be converted the corresponding (1S) diastereomers of compoundsof formulae IV, VI, VII, VIII IX and X employing the methods used inpreparing the (1R) diastereomeric compounds of those formulae.

The starting materials and intermediates are prepared by the applicationor adaptation of known methods. The compounds of formulae XIII and XIII'##STR20## wherein *, *', R₁ and Ar are as previously defined, can beobtained by a Diels-Alder reaction between a mixture of homochiralamines of formulae ##STR21## wherein *, *', R₁ and Ar are as previouslydefined, in the form of a salt, preferably with a mineral acid such asHCl, formaldehyde and cyclopentadiene working under the conditionsdescribed by S. D. Larsen and P. A. Grieco, J. Amer. Chem. Soc., Vol.107, 1768-1769 (1985). This method leads to a mixture of twodiastereoisomers. The diasteromers may be separated using L-dibenzoyltartaric acid as described by C. K. -F. Chiu in Syn. Comm., 26(3), 577(1996).

The compounds of formulae III and III' wherein R is hydrogen can beobtained by hydrogenolysis of the compounds of formula XIII and XIII' bymeans two step procedure. First the compounds are treated with2,2,2-trichlorethoxycarbonyl (Troc) chloride orβ-(trimethylsilyl)ethoxycarbonyl (Teoc) chloride to give thecorresponding Troc or Teoc derivatives (carbamates) and treating with Znin an alcoholic solvent such as ethanol with heating, or Zn in anorganic acid solvent such as acetic acid at room temperature.

The present invention is further exemplified but not limited by thefollowing illustrative examples which illustrate the preparation of thecompounds according to the invention.

In the nuclear magnetic resonance (NMR) spectra the chemical shifts areexpressed in ppm relative to tetramethylsilane. Abbreviations have thefollowing significance: s=singlet; d=doublet; t=triplet; m=multiplet;dd=doublet of doublets; ddd=doublet of doublets of doublets; dt=doubletof triplets, b=broad.

EXAMPLE 1A

Preparation of 2-(α-S-Methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene

In a 2 L reactor is charged 255 g of (S)-(-)-α-methylbenzylamine and 300mL of water. The suspension is cooled to -5° C. and a solution of 185 mLof concentrated HCl in 100 mL of water is added with stirring over onehour. The pH of the mixture is adjusted to between 5 and 6.5. Stirringis continued for 30 minutes and then 242 mL of 37% formaldehyde solutionis charged. After stirring for an additional 40 minutes, cyclopentadiene(˜270 mL) is distilled directly into the reaction mixture. The resultantmixture is stirred vigorously overnight at -5° C. The completion of thereaction is determined by high-performance liquid chromatography (HPLC).The resulting two layers are separated and the aqueous layer is washedwith 250 mL of heptane before basifying to a pH 11 with 168 mL of 50%NaOH solution and crushed ice. The organic mixture is then extractedwith 2×500 mL and 2×300 mL portions of EtOAc. The combined extracts arewashed with 200 mL of cold water, followed by 200 mL of saturated NaClsolution, dried over anhydrous Na₂ SO₄ and filtered. The clear filtrateis concentrated by rotary evaporation to yield 408.4 g (97.4%) of ayellow oil, 2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene, in adiastereomeric ratio of 77.1:22.9 in favor of the desired isomer.

¹ H NMR (500 MHz, CDCl₃): δ 1.35 (d, 2H); 1.46 (d, 1H); 1.62 (d, 1H);2.89 (d, 1H); 3.05 (m, 1H); 4.13 (s, 1H); 6.11 (d, 1H); 6.32 (m, 1H);7.26 (d, 2H); 7.33 (d, 2H); MS (El, 70eV) m/z (relative intensity): 199(M+, 70)

EXAMPLE 1b

Preparation of 2-(α-S-Methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene

Into a 250-mL three-necked flask equipped with a cooling apparatus andstirring system, a solution is introduced under an argon atmosphere,which solution consists of 20 g of (S)-(-)-α-methylbenzylamine (165mmol) in 60 mL of water whose pH is adjusted to 6.1 by the addition of17 mL of 36% HCl (W/V). After cooling to 5° C., 20 mL of a 37% (W/V)aqueous formaldehyde olution are added. The solution is stirred for 5minutes at 5° C.; then 21.8 g of cyclopentadiene (330 mmol) are added.The mixture is stirred for 16 hours between -5° and 0° C. The aqueousphase is separated by decanting and then washed with 50 mL of pentane.Neutralization to pH 8 is achieved by addition of concentrated NaOH. Twoextractions are then carried out, each with 70 mL of EtOAc. The pH ofthe aqueous phase is adjusted to 11 by the addition of concentratedNaOH, followed by two extractions, each with 70 mL of EtOAc. The organicphases are combined, and then washed two times with 50 mL of water, andthen they are dried over Na₂ SO₄. After filtration and concentration todryness at a reduced pressure, the yield consists of 33.1 g of2-(α-S-methyl-benzyl)-2-azabicyclo 2.2.1!hept-5-ene in the form of aslightly yellow oil.

EXAMPLE 2

Preparation of 5R,6S-Dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane

Into a 500-mL three-necked flask equipped with a cooling apparatus and astirring system, containing a solution of 20 g of2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene (75.34 mmol) in 220mL of t-butanol, 12 g of N-methylmorpholine oxide in 32 mL of water, ata temperature of approximately 25° C., are added, then 6.3 mL of a 25%(W/V) solution of osmium tetroxide (OsO₄) in t-butanol are added slowly.The stirring is continued for 2 hours at a temperature of approximately20° C., then for 3 hours at 65° C. After evaporation of the t-butanol ata reduced pressure, the residue is redissolved in 350 mL of IPA. Afterconcentration to dryness at a reduced pressure, 24 g ofcis-5,6-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane areproduced in the form of an oil. 14 g of 5R,6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane areproduced by crystallization in cyclohexane, with an isomeric purity ofmore than 95%.

The NMR spectrum, determined in deuterochloroform, shows the followingshifts (δ): 1.21 (3H, d); 1.38 (1H, d); 1.59 (1H, d); 2.22 (2H, m); 2.45(1H, dd); 2.95 (1H, s); 3.99 (1H, q); 3.78 (1H, d); 3.90 (1H, d); 7.28(5H, m).

EXAMPLE 3a

Preparation of 5R, 6S-Dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane

A solution of 0.5 mmol of a mixture (78/22 in mol) of 5R,6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane and 5S,6R-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane and 0.5mmol of L-dimethoxy-succinic acid in 1 mL of IPA is stirred for 24 hoursat a temperature ranging from 25° C. at the beginning to 5° C. Thecrystals obtained are separated by filtration and dried. One thusobtains 110 mg of 5R, 6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo2.2.1 !heptane with an enantiomeric excess of 97%.

The mixture of 5R, 6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo-2.2.1!heptane and 5S, 6R-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo2.2.1!heptane (78/22 in mol) may be obtained in the following manner:

In a 250 mL three-necked round-bottom flask provided with a coolant anda stirring system, containing a solution of 7 g2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene (35 mmol) in 70 mL oft-butanol, is added, at a temperature of approximately 25° C., 4.12 g ofN-methylmorpholine oxide in 11 mL of water, then, 360 mL of a 2.5%solution (p/v) of osmium tetroxide (OsO₄) in t-butanol is slowly added.The mixture is stirred for 1 hour at a temperature of approximately 20°C., and then for 4 hours at 65° C. After the evaporation of thet-butanol under reduced pressure, the residue is taken up in 150 mL ofIPA. After concentrating until dry under reduced pressure, one obtains8.27 g of a product, the NMR spectrum of the proton of which shows thatit is composed of a mixture (78/22 in mol) of 5R,6S-dihydroxy-2-(α-S-methyl-benzyl)-2-azabicyclo 2.2.1!heptane and 5S,6R-dihydroxy-2-(α-S-methyl-benzyl)-2-azabicyclo 2.2.1!heptane.

EXAMPLE 3b

Preparation of 5R, 6S-Dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo-2.2.1!heptane

In a 50 mL one-necked round bottom flask provided with a magneticstirrer and a coolant is charged 1 g of2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!hept-5-ene (5 mmol), 2.5 mL ofdi-i-propyl ether, 2.5 mL of acetone, 0.9 mL of 58 w% aq.N-methylmorpholine oxide and 0.15 mL water. The mixture is stirred for 5minutes and 9 mg of solid K₂ OsO₄.2H₂ O is charged in once and stirringis continued at room temperature for 25 minutes. The mixture is thenstirred at reflux for 7.5 hours. HPLC shows after that time a 95%completion of the oxidation reaction. To the brown mixture cooled toroom temperature is added a solution of 630 mg of sodium sulfite in 4 mLof water. The biphasic mixture is stirred at room temperature for 1hour. Most of the organic solvents are evaporated under reducedpressure, 5 mL of di-i-propyl ether are added. The aqeous phase isseparated by decantation and reextracted by 2×5 mL di-i-propyl ether.The combined organic phases are washed with an aqueous saturated sodiumchloride solution, dried on Na₂ SO₄, filtered and evaporated underreduced pressure to yield 1.04 g (89%, corrected yield=86%) of 5R,6S-dihydroxy2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane as an oilthat precipitates on standing. The product is 95% mol. pure by ¹ H NMRin CDCl₃ (contain 4 mol. % N-methylmorpholine+0.6 mol. % startingmaterial).

EXAMPLE 3c

Preparation of 5R, 6S-Dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo-2.2.1!heptane L-tartrate

To a 2 L reactor is charged 210 g of 2-(α-S-methylbenzyl)-2-azabicyclo2.2.1!hept-5-ene, 1,200 mL of 2-methyl-2-propane and 182 mL of4-methymorpholine N-oxide. To this mixture is charged, in dropwisefashion, 8 mL of a 2.5% solution of osmium tetroxide in t-butanol. Undernitrogen the mixture is heated to 62° C. with vigorous stirring for 22hours. The reaction mixture is concentrated by rotary evaporation at 60°C. 300 mL of IPA is charged and the solution is again concentrated at60° C. to yield 246 g of 5R,6S-Dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane as a darkbrown syrup. The crude product is suspended in 1.8 L of 75% IPA at 40°C. To the suspension is added 158.2 g of L-tartaric acid with vigorousstirring. Agitation is continued at 40° C. for 2.5 hours. The mixture iscooled to 30° C., filtered, washed with 500 mL of 75% IPA and 200 mL ofIPA, then dried at 70° C. in vacuo for 16 hours to give 269.5 g of thedesired L-tartrate salt as a cream colored solid (MP 143-145° C.,diastereomeric ratio of 94.2:5.8).

¹ H NMR (500 MHz, CDCl₃): δ 1.3 (d, 3H); 2.5 (m, 2H); 4.18 (s, 2H); 7.36(t, 2H); 7.4 (t, 2H); MS (El, 70eV) m/z (relative intensity): 233 (M+,13)

EXAMPLE 4a

Preparation of 5R,6S-isopropylidenedioxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane

Into 500-mL three-necked flask, equipped with a cooling apparatus and astirring system, containing a solution of 18.4 g of 5R,6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane (76 mmol)in 130 mL of toluene, 31.7 g of 2,2-dimethoxypropane (304 mmol) and then13 g of TFA are added slowly (114 mmol). The mixture is heated for 4hours 10 minutes at 65° C. After cooling to 30° C. and concentration inthe rotary evaporator to eliminate the toluene, the excess2,2-dimethoxypropane and partially the TFA, the reaction mixture istaken up in dichloromethane, then it is neutralized by the addition of100 mL of 2N NaOH. After decanting, drying of the organic phase over Na₂SO₄, filtration, treatment with decolorizing charcoal (30 g) for 30minutes at the boiling point of dichloromethane, filtration throughClarcel® and concentration to dryness at reduced pressure, the yieldconsists of 18.8 g of 5R,6S-isopropylidenedioxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane, whose structure is confirmed by the proton NMR spectrum,which, determined in deuterochloroform, shows the following shifts (δ):1.22 (3H, d); 1.23 (6H, s); 1.31 (1H, d); 1.57 (1H, d); 2.08 (1H, d);2.34 (1H, broad s); 2.45 (1H, dd); 3.06 (1H, s); 3.40 (1H, q); 4.09 (1H,d); 4.19 (1H, d); 7.26 (5H, m).

EXAMPLE 4b

Preparation of 5R,6S-isopropylidenedioxy-2-(α-S-methylbenzyl)-2-azabicyclo- 2.2.1!heptane

To a 2-liter, 4-neck, jacketed cylindrical reactor equipped with athermocouple, overhead stirrer and condenser is charged 223 g of 5R,6S-dihydroxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane L-tartratefollowed by 1200 mL IPA. Agitation is begun and the flask charged 286 mLof 2,2-dimethoxypropane and 44.6 mL of TFA. The suspension is heated to72° C. until all the solids dissolved. After 5 hours, the reaction iscooled to 65° C. and the contents transferred to a 3 L round bottomflask. Approximately 1100 mL of solvent is removed at 48° C. and 124mbar vacuum. To the original 2-liter, 4-neck, jacketed cylindricalreactor is added 1.2 L of 2M NaOH with stirring at 25° C. To the NaOHsolution, is charged the residue from the distillation described above(˜700 mL of solution). The tan solution is cooled to 25° C. over 40minutes. Solids begin to precipitate from the solution at 28° C. Thesuspension is stirred several hours before being filtered through an 11cm Buchner funnel fitted with Whatman #1 filter paper. The filter cakeis washed with 300 mL of water. The off-white solids are slurried inwater for 13 hours and refiltered, washed with water and air dried. Thesolids are then vacuum dried at 50° C. to yield 112 g of 5R,6S-isopropylidenedioxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptaneas a white solid which according to HPLC is diastereomerically pure.

^(1H) NMR (500 MHz, CDCl₃): δ 1.28 (s, 3H); 1.27 (d, 3H); 1.39 (s, 3H);1.63 (d, 1H); 2.27 (d, 1H); 2.4 (d, 1H); 2.51 (dd, 1H); 3.12 (s, 1H);3.46 (q, 1H); 4.2 (dd, 2H); 7.28 (m, 5H); MS (El, 70eV) m/z (relativeintensity): 273 (M+, 8.4)

EXAMPLE 5a

Preparation of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo- 2.2.1!heptane

In a 250-mL three-necked flask equipped with a stirring system arecombined, 0.5 g of 5% palladium on charcoal, 5 g of 5R,6S-isopropylidene-dioxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane,3.98 g of di-t-butyl dicarbonate and 36 mL of methanol. The apparatus ispurged with argon and then with hydrogen, and then it is placed under ahydrogen atmosphere at 25° C. The reaction is continued for 5 hours bycarrying out a purge with hydrogen every 15 minutes to eliminate thecarbon dioxide formed.

After filtration through Clarcel® and concentration to dryness at areduced pressure, the yield consists of 4.84 g of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo 2.2.1!heptane,whose structure is confirmed by the NMR spectrum, which, determined indimethyl sulfoxide-d6, shows the following chemical shifts (δ): 1.16 (s,3H); 1.28 (s, 3H); 1.32 (s, 1H); 1.34 (s, 3H); 1.65 (d, 1H); 2.38 (m,1H); 2.65 (d, 1H); 2.99 (m, 1H); 3.84 (m, 1H); 3.94 (d, 1H); 4.16 (d,1H).

EXAMPLE 5b

Preparation of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo- 2.2.1!heptane

To a 2-liter, 4-neck, jacketed, cylindrical reactor equipped with athermocouple, overhead stirrer, gas bladder and a septum for nitrogenand hydrogen inlet is charged in succession; 140 g of 5R,6S-isopropylidenedioxy-2-(α-S-methylbenzyl)-2-azabicyclo 2.2.1!heptane,13.4 g of 10% Pd/C and 900 mL of methanol. The stirred suspension issparged with nitrogen for 10 minutes followed by hydrogen for 10 minutesat 25° C. This procedure is repeated every 30 minutes and the reactionis monitored by TLC (silica gel, EtOAc, visualized with iodine). After 3hours, the reaction is 50% complete according to TLC. To this partiallyreduced solution is charged 56 g of di-t-butyidicarboxylate over 10minutes followed by a nitrogen/hydrogen sparge as described above. Every30 minutes, an additional 10 g of di-t-butyldicarboxylate is added,followed by a nitrogen/hydrogen sparge until a total of 112 g ofdi-t-butyldicarboxylate is added (56 g plus 10 g charges). The reactionmixture is stirred overnight at 25° C. The Pd/C suspension is filteredthrough a 9 cm Buchner funnel fitted with #54 filter paper and a bed of5 g of Celite and the reactor and filter cake are washed with 100 mL ofmethanol. The filtrate is placed in 2 liter 1-neck round bottom flaskand 750 mL of solvent is removed at 40° C. and 105 mbar (˜250 mL of alight yellow solution remained). To the original reaction vessel, ischarged 1 L of water which is cooled to 10° C. The yellow residue fromthe above distillation is added to the cold water in virtually oneportion. 5R, 6S-lsopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo2.2.1!heptane precipitates from the solution as a white solid. Theslurry is stirred for 30 minutes at 6° C. before filtering and washingwith water. The resulting white solids are vacuum dried at 60° C. toyield 129.6 g of white solid which according to chiral HPLC isenantiomerically pure.

¹ H NMR (500 MHz, CDCl₃): δ 1.28 (s, 3H); 1.4 (s, 3H); 1.45 (s, 9H);1.87 (d, 1H); 2.53 (s, 1H); 2.82 (d, 1H); 3.17 (dd, 1H); 4.09 (m, 2H);4.2 (m, 2H); MS (FAB-LRP) m/z (relative intensity): 270 ((M+H)+, 9.4)

EXAMPLE 6a

Preparation of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo-2.2.1!heptan-3-one

In a 30-mL tube, 270 mg of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo 2.2.1!heptane(1 mmol) and 40 mg of RuO₂.H₂ O (0.3 Eq) are introduced. 10 mL of EtOAcand 720 mg of water (40 Eq) are added. Then, 2.14 g of sodium periodate(10 Eq) are added, and the tube is sealed hermetically. The stirring iscontinued for 16 hours at 50° C. The reaction mixture is filteredthrough Clarcel®, and then two extractions are carried out, each with 20mL of EtOAc. The organic phases are dried over Na₂ SO₄. After thefiltration and concentration to dryness at a reduced pressure, 245 mg ofa solid are obtained, containing 68% of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo2.2.1!heptan-3-one and 32% of starting material. The structure of theproduct obtained is confirmed by the NMR spectrum, which, determined indimethyl sulfoxide d₆, shows the following chemical shifts (δ): 1.38(9H, s); 1.23 (3H, s); 1.33 (3H, s); 1.85 (1H, d); 1.93 (1H, d); 2.69(1H, s); 4.24 (1H, s); 4.41 (1H, d); 4.51 (1H, d).

EXAMPLE 6b

Preparation of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo-2.2.1!heptan-3-one

To a 2 liter 4-neck jacketed cylindrical reactor equipped with athermocouple, overhead stirrer, and condenser is charged in succession:120 g of 5R, 6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo-2.2.1!heptane, 0.3 g of RuO₂, 201.2 g of sodium bromate, 960 mL ofEtOAc, and 1000 mL of water with stirring. The reaction mixture isheated to 45° C. and stirred at this temperature for 15 hours. Thestirring is discontinued and the aqueous layer discarded. Saturated NaCl(500 mL) is added to the reaction vessel and the suspension is stirredfor 10 minutes. Stirring is again discontinued, the layers are allowedto separate and the aqueous layer removed. A 33% maleic acid disodiumsalt solution (500 mL) is charged to the reaction vessel, the suspensionstirred for 5 minutes and the layers again separated. The organic layeris then filtered through a bed of Celite to remove the catalyst and thesolvent is removed in vacuo. The resulting solid is dried in a vacuumoven to yield 117 g of 5R,6S-isopropylidenedioxy-2-(t-butoxy-carbonyl)-2-azabicyclo2.2.1!heptan-3-one as a white solid contaminated with 5% startingmaterial. A 115 g sample of this material is dissolved in 350 mL ofheptane at 85° C. and allowed to cool to 25° C. over about 3 hours thento 5° C. before filtration and drying in vacuo at 60° C. 92 g (74%) of5R, 6S-isopro-pylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo-2.2.1!heptan-3-one is obtained as a white crystalline solid.

¹ H NMR: δ 1.32 (m, 3H); 1.48 (m, 12H); 1.82 (m, 1H); 2.1 (m, 1H); 4.43(m, 1H); 4.48 (m, 1H); 4.6 (m, 1H); MS (FAB-LRP in nitrobenzyl alcohol):284 ((M+H)+, 10%)

EXAMPLE 7a

Preparation of 2R,3S-isopropylidenedioxy-4R-amino-1S-ethylaminocarbonyl-cyclopentanebenzoate

In a Berghoff tube is placed 568 mg of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo2.2.1!heptan-3-one and 10 mL of a 70% aqueous solution of ethylamine (byweight). The mixture is heated for 4 hours at 60° C. while stirring.After cooling, the excess ethylamine and water is eliminated underreduced pressure. After drying under reduced pressure, one thus obtains98% yield of 650 mg of 2R,3S-isopropylidenedioxy-4-R-t-butoxy-carbonylamino-1-S-ethylaminocarbonylcyclopentane, the structure of which is confirmed by the NMR spectrum ofthe proton, and the rotatory power of which is a!^(D) ₂₀ =15.0 (c=1;methanol).

To a solution of 200 mg of 2R,3S-isopropylidenedioxy-4R-t-butoxycarbonylamino-1-S-ethylaminocarbonylcyclopentane in 1.6 mL of anhydrous dichloromethane is added 275 mL ofTFA. The mixture is stirred overnight at a temperature of approximately-5° C. The reaction mixture is poured into 4 mL of 2.5N aqueous sodiumcarbonate. The organic layer is concentrated under reduced pressure at atemperature below 25° C. One thus obtains 125 mg of a product which isdissolved in 0.5 mL tetrahydrofuran. To this solution is added 70 mg ofbenzoic acid. After cooling the solution obtained to a temperature ofapproximately 0° C., the crystals obtained are separated by filtrationand washed in pentane. One thus obtains 138 mg of 2R,3S-isopropylidenedioxy-4R-amino-1S-ethylam inocarbonyl cyclopentanebenzoate.

EXAMPLE 7b

Preparation of 2R, 3S-isopropylidenedioxy-4R-am ino-1S-ethylaminocarbonyl-cyclopentane trifluoroacetate

In a 25-mL autoclave, equipped with a magnetic stirrer, 1.47 g of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo2.2.1!heptan-3-one in a solution in 10 mL of anhydrous toluene isintroduced, followed by approximately 0.7 mL of ethylamine. Theautoclave is closed and then heated at a temperature between 90° and100° C. for 21 hours. After cooling, the toluene is evaporated, and thedissolution is carried out with 10 mL of dichloromethane and 10 mL ofwater. After decanting, the organic phase is washed with 10 mL of water.The combined aqueous layers are washed in 10 mL of dichloromethane. Thecombined organic phases are washed with 10 mL of a saturated sodiumchloride solution and then dried over Na₂ SO₄. After filtration andconcentration to dryness at a reduced pressure, the yield consists of1.58 g of a product containing 95% 2R,3S-isopropylidene-dioxy-4R-t-butoxycarbonylamino-1-S-ethylaminocarbonylcyclopentane, whose structure is confirmed by the NMRspectrum, which, determined in dimethyl sulfoxide-d6, shows thefollowing chemical shifts: 0.95 (t, 3H); 1.14 (s, 3H); 1.31 (s, 12H);1.55 (m, 1H); 2.11 (m, 1H); 2.64 (m, 1H); 3.00 (q, 2H); 3.77 (m, 1H);4.23 (m, 1H); 4.54 (m, 1H); 7.07 (d, 1H); 8.12 (t, 1H).

In a 25-mL flask, 1.22 g of 2R,3S-isopropylidenedioxy-4R-t-butoxy-carbonylamino-1S-ethylaminocarbonylcyclopentaneand 10 mL of dichloro-methane are introduced. At a temperature ofapproximately 25° C., 0.85 g of TFA is added with stirring. After 6hours of stirring and concentration to dryness, the yield consists of1.16 g of 2R,3S-isopropylidenedioxy-4R-amino-1S-ethylaminocarbonylcyclopentanetrifluoroacetate, whose structure is confirmed by the NMR spectrum,which, determined in dimethyl sulfoxide-d6, shows the following chemicalshifts: 0.79 (t, 3H); 1.03 (s, 3H); 1.19 (s, 3H); 1.42 (m, 1H); 2.05 (m,1H); 2.52 (m, 1H); 2.89 (q, 2H); 3.04 (m, 1H); 4.16 (m, 1H).

EXAMPLE 7c

Preparation of 2R, 3S-isopropylidenedioxy-4R-am ino-1S-ethylaminocarbonyl cyclopentane

To a solution of 167 mg of 5R,6S-isopropylidenedioxy-2-(t-butoxycarbonyl)-2-azabicyclo2.2.1!heptan-3-one in 1 mL of dichloromethane, cooled to 0° C., is added90 μL of TFA. The temperature is allowed to rise to 23° C. over 40minutes, then stirred for 22 hours at this temperature. Another 90 μL ofTFA is added and then stirred for another one hour at a temperature of23° C. After evaporating under reduced pressure, one obtains 123 mg of5R, 6S-isopropylidenedioxy-2-azabicyclo 2.2.1!heptan-3-one, the purityof which, determined by HPLC, is approximately 92%, and the structure ofwhich is confirmed by the NMR spectrum of the proton.

A solution of 10 g of 5R, 6S-isopropylidenedioxy-2-azabicyclo-2.2.1!heptan-3-one in 100 mL in a 70% aqueous solution of ethylamine (byweight) is heated to 110° C. for 20 hours under standard pressure. Aftercooling, the excess ethylamine is eliminated under reduced pressure,then washed with dichloromethane to eliminate the starting product thatdid not react. The aqueous layer is then concentrated and dried. Onethus obtains 10.54 g of 2R,3S-isopropylidenedioxy-4R-amino-1S-ethylaminocarbonyl cyclopentane.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof.

We claim:
 1. A method for the preparation of a lactam compound offormula ##STR22## wherein R'₁ and R"₁ independently are acyl or aroyl,or taken together form an optionally substituted methylene, and G₁ ishydrogen or an amino protecting group, comprising oxidizing a bisO-protected 1R-2-azadihydroxybicyclo- 2.2.1!heptane compound of formula##STR23## with about 0.1 mol % to about 1 mol % of RuO₂ or hydratethereof in the presence of about 3 equivalents of an oxidant to form thelactam compound with an enantiomeric excess of greater than or equal toabout 95%.
 2. The method according to claim 1 wherein RuO₂ is present atabout 0.5 mol %.
 3. The method according to claim 1 wherein the lactamcompound is formed with an enantiomeric excess of greater than or equalto about 99%.